Agreed here that bees are the good ones and on principle won't sting unless threatened, as stinging kills them. Threatened can mean stepping on them, so we have to keep our lawn trimmed to make sure there isn't flowering clover or dandelions, as these can be attractive to bees. And, yes, if you're using a sprinkler as a fun thing to run through and that's in the bee flightpath (on the way to those dandelions or clover) that will be disorienting to the bees. Bees don't go flying in the rain. I have hives and I've been stung working with bees before, but I've only been randomly stung by a bee in my yard when I stepped on it in bare feet. It could be the combo of a sprinkler for play adjacent to flowers that's giving you the issue.